Duck is the command language for the Kumo proof
assistant. Among its most important commands are proof rules, which transform
proof tasks into subtasks. Additional commands tell where the source files
for documentation are located, and provide titles and subtitles for the tatami
pages.

For each Kumo website, the Duck code that generated it is linked to its
homepage, so you can find many examples by going to the Kumo demos homepage, choosing an example, and then clicking on
the duck icon to see the Duck code that generated that website.